A piezoelectric ceramic exhibiting a so-called piezoelectric phenomenon is known in which mechanical distortion and stress are generated when an electric field is applied. Such a piezoelectric ceramic is used for a vibrating element such as an actuator, a sound generator, a sensor, or the like.
Lead zirconate titanate (Pb(Zr,Ti)O3) with excellent piezoelectricity is most frequently used as the piezoelectric ceramic used in the above way. However, since lead zirconate titanate contains a large amount of lead, the influence on the global environment such as lead elution due to acid rain is regarded as a problem recently. Therefore, there is a need for lead-free piezoelectric ceramics to replace lead zirconate titanate, and various piezoelectric ceramics without lead have been proposed according to this requirement.
On the other hand, smaller size, higher performance and higher reliability are required with the electronic components, and the same trend is also found in piezoelectric components. Bulk bodies made by a sintering method are used in most piezoelectric components, however, it occurs that processing for controlling the thickness becomes extremely difficult as its thickness becomes smaller and that the size of the crystal grain size causes deterioration of properties. As a means to solve this problem, researches on piezoelectric thin films made by various thin film forming methods and its application in the element using the same have been actively conducted in recent years.
For example, a sputtering method is a representative thin film forming method. Its mechanism is that a voltage is applied between a substrate (anode side) on which a thin film is to be deposited and a target (cathode side) made of material for film deposition which is opposite to the substrate in an inert gas atmosphere such as argon atmosphere, by which ionized rare gas atoms are forced to collide with the target which is a cathode material, and the constituent atoms of the target are knocked out by the energy, whereby a thin film is deposited on the opposite substrate.
In the film deposition using a sputtering method along with the miniaturization of electronic components, thin films with higher precision and higher quality are required. As to the requirement for thin films with higher quality, specifically, preparation of thin films with high density and less defect becomes a problem. For example, generation of particles or nodules can be listed as a reason for defects in a thin film using a sputtering method.
With the increase of the sputtering time, minute protrusions called as nodules are generated on the target surface. Arcing is generated due to the nodule during sputtering, and fragments of nodules and the like are scattered as particles at that time. If the particles adhere to the thin film, defects will be generated in that part, which may lead to defect when made into a product. Therefore, the problem that how the generation of the particles can be suppressed is required to be solved in a sputtering target.
For example, Patent Document 1 discloses a method of suppressing the generation of particles during the manufacturing of the thin film by devising a manufacturing method of a lead-based sputtering target.